Free translation APIs tested from the browser

Every translation API we tested

We ran each API on 26 October 2026 with curl and an Origin: https://example.com header from a German datacenter IP, a US residential IP and through https://proxy.cors.dev/, then in Chromium 147.0.7727.15 from http://127.0.0.1:8001. Four need no key: MyMemory, Apertium, Lingva and Google's unofficial endpoint. More browser-ready endpoints are in our list of 70 free public APIs.

MyMemory: free GET requests with a daily quota

MyMemory (https://api.mymemory.translated.net/get?q=...&langpair=en|de) takes one GET request, needs no key and sends Access-Control-Allow-Origin: *. "Where is the train station?" with langpair=en|de came back as "Wo ist der Bahnhof?".

Anonymous use is limited to 5,000 characters per day. Put a valid email address in the de parameter for 50,000 characters per day; CAT tool makers can ask to be whitelisted for 150,000. MyMemory counts the size of each request, not the number of requests, and the q parameter is limited to 500 bytes.

Call it directly, not through a shared CORS proxy. Through https://proxy.cors.dev/ MyMemory answered 429, because every proxy user shares the same quota, while direct calls returned 200.

const params = new URLSearchParams({ q: 'Where is the train station?', langpair: 'en|de' });

// A contact email raises the free quota from 5,000 to 50,000 characters a day
params.set('de', 'you@example.com');

const response = await fetch(`https://api.mymemory.translated.net/get?${params}`);
const body = await response.json().catch(() => null);

if (!response.ok || Number(body?.responseStatus) !== 200) {
  throw new Error(`MyMemory failed: ${body?.responseDetails || response.status}`);
}

console.log(body.responseData.translatedText);

Google Cloud Translation with a website-restricted key

Google Cloud Translation Basic (https://translation.googleapis.com/language/translate/v2) includes the first 500,000 characters per month free, applied as a $10 monthly credit shared with the Advanced edition, then charges $20 per 1,000,000 characters. It echoes your Origin on GET and POST and answers preflight requests, so fetch() works directly.

In the Google Cloud console, restrict the key to your website (HTTP referrers) and to the Cloud Translation API. A Referer header can be faked outside a browser, so the restriction stops other websites from using your key, not a script that copies it from your bundle. You don't need a proxy here, and the cors.dev free tier refuses URLs with key= anyway (HTTP 400, X-Cors-Error: credential_in_url).

// Restrict this key to your website and to the Cloud Translation API in the Google Cloud console
const apiKey = 'YOUR_WEBSITE_RESTRICTED_KEY';

const params = new URLSearchParams({
  key: apiKey,
  q: 'Where is the train station?',
  target: 'de',
  format: 'text',
});

const response = await fetch(`https://translation.googleapis.com/language/translate/v2?${params}`);
const body = await response.json().catch(() => null);

if (!response.ok) {
  throw new Error(`Google Translate failed: ${body?.error?.message ?? response.status}`);
}

const [{ translatedText, detectedSourceLanguage }] = body.data.translations;
console.log(detectedSourceLanguage, '->', translatedText);

DeepL needs a backend

DeepL (https://api-free.deepl.com/v2/translate) sends no CORS headers. Its preflight answered 204 without Access-Control-Allow-Origin, and Chromium 147 reported: Access to fetch at 'https://api-free.deepl.com/v2/translate' from origin 'http://127.0.0.1:8001' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. If the same call works in your terminal, here is why curl and Postman behave differently.

That is deliberate. DeepL's docs say the API does not allow calls from browser-based apps, tell you never to reveal your key in public code, and point you to your own backend. Keep the DeepL key on your server behind a small API proxy for your frontend, never in the browser or a public proxy.

The free tier changed too. Existing DeepL API Free accounts still get 500,000 characters per month, but the plan can no longer be purchased. New users get the Developer plan: a one-time 1,000,000 characters that does not reset. Each request can be up to 128 KiB.

Microsoft Translator and LibreTranslate

Microsoft Translator (https://api.cognitive.microsofttranslator.com) has a free F0 tier of 2 million characters per month, standard translation and custom training combined, with up to 50,000 characters per request. It sends Access-Control-Allow-Origin: *, its preflight allows the key header, and /languages needs no key. Authenticate with an Ocp-Apim-Subscription-Key header or a Bearer token from https://api.cognitive.microsoft.com/sts/v1.0/issueToken, valid for 10 minutes. Keep the subscription key on your backend and hand the browser short-lived tokens.

LibreTranslate is open source and free to self-host, and it sends Access-Control-Allow-Origin: * with a preflight that allows Authorization and Content-Type. The hosted libretranslate.com is paid only: POST /translate without a key returned 400 {"error":"Visit https://portal.libretranslate.com to get an API key"}. Plans cost $29 per month (bursts up to 80 calls per minute, about 20 sustained, 2,000 characters per call) or $58 for 200 calls per minute, with no free trial and a 7-day money-back guarantee. For a free browser setup, run your own instance and call it directly; keep a paid hosted key on your backend.

Apertium, Lingva and unofficial Google endpoints

• Apertium (https://apertium.org/apy/translate?q=...&langpair=eng|spa): free, open-source, rule-based translation with no key and Access-Control-Allow-Origin: *. /listPairs returned 133 language pairs, and "Hello world" in eng|spa returned "Hola Mundo". No quota is published.
• Lingva Translate: an open-source front end for Google Translate built on a Google Translate scraper, with GET /api/v1/:source/:target/:query on each instance. None of the public instances we tried worked: lingva.ml returned 403 to our datacenter IP and untranslated text through the proxy, lingva.lunar.icu and translate.plausibility.cloud returned 500, and lingva.garudalinux.org returned 403.
• Google's translate_a endpoint (translate_a/single?client=gtx): undocumented, no terms, no SLA. curl from our datacenter IP, a residential IP and the proxy got 429 "Sorry" pages, while Chromium 147 got 200 with CORS headers on both networks. Google can change or block it at any time, so keep it out of production.

Good questions.